A conventional technique for obtaining tissue samples from deep within the body is aspiration biopsy. Aspiration biopsy is safe and minimally traumatic, utilizing a small, hollow needle which is inserted directly into the body, to a desired point, whereupon a tissue sample is withdrawn by vacuum aspiration. The aspiration needle is then withdrawn, and because of its relatively insignificant diameter, allows for wound closure by normal muscular and tissue tension, without the need for sutures, cauterization, or the like.
For effective aspiration biopsy, the tip of the needle must be accurately placed at the location of the tissues to be sampled, and it is a primary object of the present invention to provide means and methods for facilitating such placement.
A similar approach is utilized for location and removal of tissue lesions, such as in the breast. That is, with the aid of X-rays or the like, a needle is inserted into the breast until its tip is at the approximate location of the suspected lesion. The surgeon is thereby guided in order to perform a biopsy or other surgical procedure. This technique too suffers from dimensional/accuracy limitations associated with X-rays, and it is an object of the present invention to provide means and methods for facilitating such placement.
Ultrasound techniques have provided an excellent modality for in vivo imaging of relatively deep soft body tissue, offering conventional A-mode, B-mode, and C-mode approaches. Application of the A-mode to aspiration techniques is possible, wherein the needle is introduced down the center of the beam, through a hole in the transducer, and the needle tip is seen as a reflection due to the discontinuity of the ultrasound field at the needle tip. A-mode is not the preferred diagnostic approach, however, due to the relatively smaller information content of its output. Real time ultrasound imaging is available through a variety of B-mode and C-mode scanning techniques, such as moving, multiple, or phased array transducers, but these are relatively less suitable for aspiration techniques because the likelihood is great that an ultrasound pulse will have a non-perpendicular incidence to the aspiration needle point, and thereby not be reflected back to the transducer.
Hence, prior art approaches to ultrasound imaging of aspiration techniques are generally unsatisfactory, including A-mode aspiration transducers wherein the needle is introduced down the center of the beam by means of a hold in the transducer, and B-mode schemes wherein the needle is sought to be maintained perpendicular to the axis of propagation of the transducer.
It is an object of the present invention to provide ultrasound--aspiration systems and techniques whereby the former imaging modality and the latter biopsy technique are rendered mutually compatible, especially for real time B-mode or C-mode imaging systems, and including those which employ moving transducers.
It is a further object of the present invention to provide ultrasound systems and techniques whereby needle localization such as for breast lesions or the like is facilitated and rendered substantially more accurate.